The Fit Ball Is One Of The Most Under Utilised Training Tools And Used Correclty Can Increase Your Resistance Workouts By Increasing Your Balance, Mobility And Flexibility. It Will Strengthen Back, Spinal And Abdominal Muscles And Improve Posture. Why? Because You Are Working On An Unstable Surface So You Need To Work Your Abdominal Muscles While Performing Your Exercises. For Example: Performing Bicep Curls On A Fit Ball Requires You To Sit Up Straight, Improving Your Posture And Ensuring Your Abdominals Muscles And Back Musscles Are Switched On. So You Are Working Much Harder Than Just Sitting On A Bench And Performing The Sane Action. Thus Increasing Their Workout Dramatially.You Can Also Increase Or Reduce The Instability Whilst Sitting On The Fit Ball By Bringing Feet In Closer Or Feet In Wider By Increasing Your Base Of Support.